Integrating a mud pulse telemetry valve into a measuring while drilling (MWD)/logging while drilling (LWD) System is sometimes cumbersome and expensive due the tight mechanical spacing tolerance requirements of the system components. Mechanical, electrical, and hydraulic connections must be maintained.
Components of these systems are prone to mechanical wear because they include moving parts that are placed directly in the drill string's fluid flow path. The parts of this system are designed to generate pressure pulses so they purposely disrupt flow and are exposed to very high velocity abrasive media. Additionally, in some designs, interchangeable components that disrupt the drilling fluid flow are configured for very specific drilling fluid flow rates. Occasionally, these configurations require adjustment at the rigsite.
Additionally, drill stem members, i.e., drill pipe and drill collars, that house or are a part of the mud pulse telemetry valve can include threaded joints that can become damaged. The likelihood of thread damage is high because of the materials typically used in these devices and the large mass of these members which require heavy machinery to handle and torque the members together. The damaged members sometimes require replacement. Sometimes, damaged threads can be re-machined (“cut back”) to restore their condition and extend the useful life of the very expensive drill stem member. This re-machining, however, changes the length of the member and can inadvertently change the mechanical spacing between the system components of the mud pulse telemetry valve requiring the replacement of the drill stem member.
Because of the tremendous investment already made in drill pipe and drill collars, it is highly desirable that the mud pulse telemetry valve be compatible with existing drilling equipment and require minimum or no modification to the drill pipe and drill collars. Mud pulse telemetry is known to offer an effective solution since it does not rely upon electrical wiring extending to the surface, or other mechanisms which may necessitate modification to existing hardware. Mud pulse telemetry propagates signals through the drilling fluid flowing in the drill string to the surface at the speed of sound, thereby providing a very fast communication link to the surface. Mud pulse telemetry is usually in the form of a valve located in the vicinity of the drilling bit, which intermittently restricts the flow of drilling fluid within the drill string. The mud pulse telemetry system may be lowered on a wireline located within the drill string, but is usually formed as an integral part of a special drill collar inserted into the drill string near the drilling bit.
A continuous column of drilling fluid is circulating within the drill string from the surface of the well to the drill bit at the bottom of the well during normal drilling operations. The basic operational concept of mud pulse telemetry is to intermittently restrict the flow of drilling fluid as it passes through the downhole telemetry valve, thereby creating a pressure pulse in the flow of the drilling fluid that travels to the surface of the well at the speed of sound through the drilling fluid. The information sensed in the vicinity of the drilling bit, which is to be transmitted to the surface, is encoded into a digital format and that digital formatted signal is used to intermittently actuate the downhole telemetry valve which restricts the flow of drilling fluid in the drill string, thereby transmitting pulses to the surface. The pulses are detected at the surface and transformed into electrical or other signals which can be decoded and processed to reveal transmitted information. In a typical oil or gas well, drilling fluid is circulated through the interior of the drill pipe at flow rates of about 100 to about 1200 gallons per minute. The mud pulse telemetry system must operate to partially restrict this flow. Therefore, the system must control large amounts of energy. The downhole telemetry valve must operate quickly to create a pressure pulse in this high pressure environment to intermittently restrict the flow of drilling fluid. This restriction must be sufficient to create a pressure rise in the flow stream that will be detectable at the surface of the well. At the typically high flow rates of drilling fluid, considerable force and energy are required to actuate the downhole telemetry valve in the manner necessary to create the desired pressure pulses.
Accordingly, there exists a need for a downhole valve capable of effectively transmitting downhole data or operating a downhole tool while reducing repair and maintenance costs. The inventive concepts disclosed herein are directed to such a downhole valve that, in some embodiments, can be characterized and/or used as a mud pulse telemetry valve.